Extraction process



Dec. 6, 1938. s. TIJMSTRA EXTRACTION PROCESS 2 Sheets-Sheet l Filed May 27, 1935 De 6, 1938- s. TUMSTRA EXTRACTION PROCESS 2 Sheets-Sheet 2 Filed May 27, 1935 |||||||YI l.

Patented Dec. s, 193s PATENT ori-lcs Ex'rascrron raooess Sijbren Tiimstra, Berkeley, Calif., assigner to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application May 27, 1935, Serial No. 23,557?.

1l Claims.

This invention relates to an improved process for the solvent extraction oi liquid mixtures, and more` specically comprises an improvement thereof in which two mixtures of different boil- 5 ing ranges are extracted simultaneously in a manner that the presence of the lower boilirlar mixture causes a more complete and' eiiicientg Separation of the components of the mixture.

In the extraction of lubricating oil distillates lo or residues it is desired to recover paranic hydrocarbons which are the most' stable against deterioration and which possess the most desirable temperature-viscosity characteristics. 'In the known processes for extracting hydrocarbon l1 mixtures, Asuch as cylinder oil, lubricating oil, transformer oil, spindle oil, solar oil, kerosene, gasoline, etc., a solvent having a preferential solubility for non-parainic components is contacted withl the hydrocarbon mixture under con- 20' ditions of temperature, pressure, and concentration to cause the formation or a rainate phase, and an extract phase, which are then separated and treated to remove the solvent from the separated phase and yield the ranate and extract portions. The parafnic components of the mixture are thereby concentrated in the railinate and the non-paraliinic components are concentrated in the extract By repeatedly extracting the rafnate or the raflinate phasewith a fresh solvent,

suicient length or of a suflcient number of stages, an ultimate ramnate of any desired degree of purity can be produced, but the yield will often be very low because considerable amounts oi the 35 less soluble or parainic components are dissolved in the solvent and are removed from the extraction system as a part of the extract phase.

As an improvement on this process, it has been proposed to treat the extractor the extract phase Dloyed. Y

In such processes the solvent for paramnicrractions (hereinafter designated as the auxiliary .55 Y solvent) Y must be supplied to the system and is not or by treating it in a countercurrent treater of to remove from it certain portions of the paramnic components, which portions may either be returned to the extraction zone or be withdrawn as such solvent pairs, as liquid sulfur dioxide and' propane, or bi-sulde and methyl alcohol, are em- (Cl. ISG-13) itself improved by the treatment. It is, therefore, an added item in the costs of the installation `and operation.

In accordance with my invention, I have found that it possible to use as the auxiliary sol-vent a low boiling hydrocarbon having a paraflnc content which is sufficiently great to cause it to be at least partially immiscible with the extract phase. In such a treatment the low boiling hydrocarbon serves the function of the auxiliary solvent, in that it washes out of the oil extract phase a portion of its paran-mic constituents. At the same time this low boiling hydrocarbon mixture is itself separated into raffinate and extract portions, whereby the high boiling and low boiling hydrocarbons are simultaneously extracted. It is often desirable to operate this process at temperatures which are below those which would be employed in the absence of the low boiling v hydrocarbon. m this manner the cost of providing an auxiliary solvent mixture is effected at claims. It is understood that the drawings are,

however, exemplary only because my invention may be practiced in a large number of methods, and the individual steps may be re-arranged in many ways. without departing from thespirit and scope of the invention. Furthermore, my invention may be applied to many forms of apparatus other than those suggested in the drawings.

In the drawings,fFigure l is a schematic diagram illustrating one embodiment of my invention; Figures 2, 3 and 4 are similar diagrams illustrating modiled embodiments thereof. The.

same numerals designate the same elements in al1 of the ngures. Y

in the drawings, Ynumerals '.i and 6 Vrepreserd: extraction apparatus which may bel'singleor multi-stage continuous countercurrent treaters, although a batch method be employed. Moreoveni and E may be portions oi the same vertical liquid contact chamber, provided with means` for introducing the feed, and, when necessary, as inthe methods which isunsusceptible of improvement is eliminated, andthe extraction oi- 50. of operation may also solved in the second railinate phase.

of Figures 2, 31ml .4, for withdrawing all or portions of one of the'liquld phases at an intermediate point. Numerals 1, l and 9 represent sources of a selective solvent, of the high boilingoiltobeextracted,andthelowboilingdis tillate to be extracted. Pipe conduits and other apparatus will be described Ain the course of the explanation of the peraon of the process. it being understood that the apparatus may be equipped with suitable pumps, valves, heat-exchangers, and other adjuncts which are not specifically recited.

. Referring particiuariy to Figure 1, the mghboiling oli is subjected to an extraction with a selective solvent fed to the apparatus i by means of a conduit Il, preferably by llowing it countercurrently to the solvent. The solvent may consist of a. pure solvent,.such as suliur dioxide, 'dichloroethyl ether, furrural, quinoline, phenoi, nitrobenaene, `etc..`or of mixtures of said solvents. It is, moreover, often advantageous to employ an aromatic hydrocarbon (monoor poly-cyclic) diluent i'or the selective. solvent, to increase the solvent power of the solvent and to improve the composition of the raiilnate phase. Such a diluent may be added separately into the apparatus i, or mixed with the solvent outside of said apparatus. as by maintaining a properly blended solvent-diluent mixture in the tank 1.

The raflnate phase and the extract phase formed in the apparatus I are withdrawn through pipes Il and I2, and are, for convenience, hereinai'ter designated as theiirstraiilnate phase and the iirst extract phase, respectively. The latter will generally-contain substantial amounts or the less soluble or paraiiinic components of the.

oil which It is desired to-recover asa part of the raiinate phase; -'Io recover these desirable constituents this first extract phase is fed into apparatus 6 where it is contacted with a distillate having a lower` boiling range than the oil which was introduced at. 8. The extraction apparatus 6 may be similar'to the apparatus 5 in that it.`

may consist or a vertical chamber provided with suitable contact means.. such as packing, or it may be constructed' in the i'orm of a series of alternating mixing and settling means interconnected for counterilowing the low boiling distillate from I andthe iirst extract from I2.

The low boiling distillate should be suiilciently paraiilnic in nature to be partially insoluble in the irst extract phase and to cause the formation of second ramnate and extract phases. Under these conditions portions 'of the paraillnic components of the high boiling oil vwhich are present in the rst extract phase will be dis- At the Vsaine time the low boiling distillate will be separated into paramnic and non-parailinic. portions, most of the former entering the second raiiinate phase, while the latter is largely dissolved in the solvent and-forms a part of the second extract phase. The second raiiinate phaseis withdrawn at I2 and introduced into the apparatus 5 either together with the high boiling feed, as shown, or separately. The lrst ramnate phase in the pipe Ii, consisting of selective solvent and parail'lnic concentrates or railinates of each of the two feed mixtures may be treated in 'the fractionating apparatus Il to separate it into three or more portions.- The solvent is withdrawn and returned-to the storage I through a pipe i5 and a condenser I6. Although I have shown only a single conduit for the solvent, when an aromatic diluent is employed it may often be diluent. 'Ihe low boiling and high boiling railinates may be recovered as distillation products from the -fractionating apparatus I l and withdrawn at i1 and II. If desired, a portion of the low boiling railinate from i1 may be recycled through a conduit i and introduced to apparatus I together with the low` boiling distillate introduced at I. This will increase the parafnieity of the feed mixture introduced at this point.

The second extract phase is withdrawnl at 2li and fed into a iractionating apparatus 2l where it is separated into solvent, low boiling extract, and high boiling extract portions, which are withdrawn at 22, 23 and 24, respectively, the solvent being returned to the storage 1, as shown. A portion of the high boiling extract, or of va mixture of high and low boiling extracts may, if desired, be recycled to the extraction apparatus 6 as through a conduit 24', and used as a backwash, thereby further improving the purity of the extract phase in the conduit 20, i. e., reducingits content of paraiinic constituents. This feature is more fully described in the patent to van Dijck, No. 2,081,719.

It is oftenpossible to use the low boiling extract withdrawn at 23 instead of or in conjunction with the aromatic diluent for the selective solvent. This may be eiiected by withdrawing at 25 only a portion oi' the distilled low boiling extract, and feeding the remainder through a valve 26 and pipe 21 into the apparatus v5, either together with the selective solvent in pipe I0, as shown, or separately. 'I'his low boiling extract will improve the composition of the high boiling raillnate.

When a high boiling rafiinate of a high degree of purity is desired it is advantageous to employ an aromatic diluent for the selective solvent, and to exclude parafilnic diluents from the last stage or stages of the extraction process, by which is meant the stage or stages nearest the point at which the high boiling raiilnate phase is with?- drawn. This method of operation is illustrated in Figure 2, in which the second raffinate phase from the apparatus E, instead of being introduced 2l toA separate it into solvent, low boiling, and

-high boiling portions, which are withdrawn at 2l, 2li and Il, respectively. 'Ihe low boiling product will be somewhat more parailinic in nature than the feed which is introduced at 9, and may be continuously withdrawn as the low boiling raiiinate. If desired, a portion of it may be recycled to the feed through a conduit I9, as explained above in connection with Figure 1. The high boiling portion is introduced into the apparatus 5 with the high boiling feed at 8. The solvent from 29 is preferably returned to the storage 1, although a. portion of it may be recombined with the high boiling fraction in conduit 3i and introduced into the apparatus 5 in a manner not shown in the drawing. The raiilnate phase withdrawn at Il is treated in the frac tionating apparatus il' to separate it into solvent, low boiling, and high boiling portions, which are withdrawn at i5, i1 and i8, respectively, as described above in connection with Figure 1. Since low boiling paranic constituents have been excluded from the apparatus 5, the distillation product recovered at i1 will be recovered in relatively small quantities and be largely aromatic,

GII

but not to the same degree as the product which is recovered at 23. It may be withdrawn as a separate product, or blended with a small part of the product from 30 to increase its parafnicity and then introduced into the apparatus 6 together with the low boiling'feed at 9. In either of the above described modes of operation in which a portion of the low boiling extract is recycledthrough the conduit 21 and used as a solvent diluent, its presence in large amounts in contact with 'a rainate phase which is to yield a low boiling raffinate reduces the purity or paraiinicity of this low boiling ramnate. Thus, in the method of Figuresl and 2, when valve'26 is opened to recycle aromatic extract the products auxiliary extraction zone for further extracting the low boiling extract. v Such an Aarrangement is illustrated in Figure 3, in which elements designated by reference characters to 3, to I6 and 8 to 2l, inclusive, are

similar to corresponding elements in Figure l. The low boiling distillate recovered from the i fractionating apparatus I4 at Il" is fed into an extraction apparatus 3| which may be similar to the apparatus 5 and may comprise a single or a plurality of stages arranged to eiect countercurrent contact between selective solvent introduced from storage l through a pipe 32. The conditions in the apparatus 3| are such that two phases will be iformed; the extract phase being introduced into the apparatus 5 at It to extract the high boiling feed. It is generally most desirable to introduce all of the fresh solvent by wayv of the pipe conduit 32 and extraction zone 3|. If, however, it is desired to employ a smaller quantity of solvent in the apparatus 3|, additional solvent may be introduced through a pipe 33 directly into the. apparatus 5.

The raffinate phase from the apparatus 3| is withdrawn at 34 and treated in fractionating `rafliate will, under these conditions, be highly paraiiinic.

It is, moreover, possible to eliminate the fractionating apparatus |4, and feed the rst raiiinate phase from the apparatus 5 directly into the apparatus 3| through a conduit In this method the high boiling raffinate is recovered at 38 as a product of the fractionating apparatus 35.

A further modification of my process for producing, a highly paraiiinic low boiling product while recycling a portion of the low boiling aromatic extract is illustrated in Figure 4, in which reference characters 5 to I2, IEN@ and I8 to 21 designate elements which are similar Vto those of Figure 3. In this method the low boiling parailinic substance is excluded from the stage in into an auxiliary extraction apparatus 39, which Amay be similar to theapparatus 5, in which it is contacted, preferably in countercurr'ent, with solvent introduced through a pipe40, under ,con-

. 1- ditions to produce railinate and extract phases.

The former, containing the parailinic components of both of the hydrocarbon mixtures and a. small amount of solvent is withdrawn at 4| and treated in a fractioning apparatus 42 to separate its components. 'I'he solvent Ais withdrawn at 43 and returned to storage 1, and the low boiling rainate is withdrawn at 44. Since substantially no low boiling extract has been introduced into the apparatus 39, this raffinate will be highly parafilnic.

The high boiling fraction contained in the phase withdrawn at 4| is' recovered from the fractionating apparatus 42 at 45 and fed into the apparatus 5 together with the high boiling feed, and extracted with all or a portion of the extract phase which is withdrawn from the apparatus 39 at 46 and introduced into the apparatus 5 through a conduit Ill'. Although it is generally desirable to introduce all of the solvent by way of the pipe 40 and the extraction zone 39, it may at times be advantageous to introduce additional quantities of fresh solvent directly into the apparatus 5 through a conduit 4l. There being substantially no low boiling parainic diluent in the apparatus 5, the rafnate phase which is withdrawn at M Will contain the high boiling fraction in a highly parafnic condition. This ramnate phase is fed into a fractionating apparatus I4 where it .is separated into solvent, low boiling, and high boiling portions, 'which are withdrawn at l5, ll' and 3, respectively, and disposed of as discussed above in connection with Figure 2.

Ii desired, .all or a` portion of the extract phase withdrawn at 45 may be continuously withdrawn through a pipe 48, and fractionated in the apparatus 49 into a solvent portion which is withthe conduit Illy', together with solvent from conduit 50 or 4l, in a manner not shown in the drawings. In this manner the low boiling product.

, which is not suiciently aromatic to cause the de sired improvement in the distribution in the apparatus 5 may be separated at this point.

Myv invention may be used for the simultaneous extraction of any two hydrocarbon mixtures having different boiling ranges. The process is especially applicable for the production oflubrieating or transformer oils as the high boiling raiiinate, employing gasoline, keresene or a similar light distillate as the low boiling feed mixture. Such mineral oil hydrocarbons generally consist of paraiiinic, naphthenic and aromatic components, the last two components being often categorically designated as naphthenic components. In the present claims I use the term non-parafiinic to include both of these types of hydrocarbons.

As used in the present specication and claims, I use the term components to designate portions of any liquid mixtures which exhibit different chemical or physical properties, and which can be separated from each other with a solvent mixture. It will be evident that by the word component is not meant only one chemically pure substance, but that this word covers also a mixture of substances. A component is said to be pure ifA it does not contain any portion of a sub- I claim as my invention:

1. A process of concentrating the parafilnic component of a highboiling mineral oil containing paraifinic and non-parafflnic components comprising the steps of extracting said oil with a slective solvent for non-parailinic components in a first extraction zone under conditions producing first raffinate and extract phases, separating the first extract phase from the first rafnate phase, contacting the first extract phase in a second extraction zone with a low boiling mineral oil distillate containing parafiinic and nonparafiinic components under conditions causing the formation of a second raffinate phase comprising parafiinic components of the said oiland of the low boiling distillate, and a second extract phase comprising non-paraiiinic components of the said oil and of the low boiling distillate, separating the second extract phase from the second raffinate phase, returning atleast a portion of the second raiiinate phase tothe first extraction zone, separating from the second extract phase a non-parafnic low boiling extract, introducing at least a portion of said separated low boiling extract into the first extraction zone, Withdrawing the first raiiinate phase from the first extrac- Y tion zone, and separating from said first raffinate phase a fraction containing the paraiiinic component of the high boiling oil in concentrated form.

2. A process of concentrating theparai1inic component of a high boiling mineral oil containing parafiinic and non-parafiinic components comprising the steps of extracting said oil in countercurrent with a selective solvent for nonparainic components,A in a first extraction` zone under conditions producing first raffinate and extract phases, separating the first extract phase from the first ramnate phase, contacting the first extract phase in a second extraction zone with a low boiling mineral oil distillate containing parafiinic -and non-paraiiinic components under conditions causing the formation of a second raflinate phase comprising parafinic components of the said oil and of the low boiling distillate, and a second extract phasel comprising non-paraiiinic components of the said oil and of the low boiling distillate, separating the second extract phase from the second raffinate phase, returning at least a portion of the second raffinate phase to theiirst extraction zone, sepparafiinicy low boiling extract, introducing at least a portion of said separated low-boiling ex- .Y

tract into the first extraction zone near the point of introduction of thesolvent, withdrawing the first raffinate phase from the first extraction zone, and separating from said first' raffinate phase a fraction vcontaining the paraiiinic component of the high boiling oil in concentrated form.l

3. A process of' separating mineral oil fractions containing paraillnic and non-paraiiinic components into two portions., respectively, more paraflinic and less paramnic than the original fractions, comprising the steps of counterfiowlng a selective solvent and a low boiling mineral oil distillate adapted to form separate layers when in contact with each other, said selective solvent having a greater solvent power for nonparamnic hydrocarbons .than for paraflinic hydrocarbons,and the low boiling distillate containing paramnic and non-parafiinic components, bringing a separate body of a high boiling mineral oil containing both parafflnic and non-paraffinic hydrocarbons into contact with the counterfiowing solvent and low boiling distillate, thereby producing raflinate and extract phases, withdrawing said extract phase and separating from it a non-paraflinic low boiling extract, introducing at least a portion of said separated low boiling extract into the stream of said selective solvent at a point to flow countercurrently to said high boiling mineral oil, withdrawing the raffinate phase, and separating from it a fraction containing the parafiinic component of thev high boiling fraction in a concentrated form.

4. A process of separating mineral oil fractions containing parafflnic v and non-paraffinic components into two portions, respectively, more parainic and less parailinic than the original fractions, comprising the steps of extracting a high boiling mineral oil in a first extraction zone by flowing it countercurrently to a selective solvent having a greater solvent power for nonparafiinic hydrocarbons than for paraflinic hydrocarbons, thereby producing first extract and raffinate phases, separating the first rafiinate and extract phases, fiowing said first extract phase in a second extraction zone countercurrently to a low boiling mineral oil distillate containing paraffinic and non-parafiinic components under conditions causing the formation of a second raffinate phase comprising parafiinic components of the oil and of the low boiling distillate, and a second extract phase comprising non-parainic components of the oil and of the low boiling distillate, returning at least a portion of the second raffinate phase to the first extraction zone near the point of introduction of the said oil, withdrawing the second extract phase from the second extraction zoneand separating from it an extract comprising the non-paraffinic component of the low boiling distillate in concentrated form, introducing at least a portion of said separated low boiling extract into the first extraction zone near the point of introduction of the solvent, Withdrawingflrst raffinate phase from the first extraction zone and separating from it a fraction containing the parafiinic component of the high boiling oil in a concentrated form.

5. A process of separating a high boiling mineral oil containing parailinic and non-paraffinic components into two portions, respectively, more paraflinic and less paraiflnic` than the original oil, comprising the steps of extracting said oil in a first extraction zone with a selective solvent having a greater solvent power for nonparaiilnic hydrocarbons than for parafllnic hydrocarbons, thereby producing rst rafiinate and extract phases, separating the first raffinate and extract phases, contacting the -first extract phase in a second extraction zone with a low boiling mineral oil distillate containing parafflnic and nonparaiilnic ,components under conditions causing the formation of a second raffinate phase comprising paraflinic components of the said oil and of the low boiling'distillate, and a vsecond extract phase comprising. said non-parammc components of the oil and of the low boiling distillate, separating the second extract phase from the second raffinate phase, removing from at' least a portion of the second raffinate substantially all of the low boiling distillate, returning at least the high boiling oil constituent of the residual portion 'of said second raffinate phase to the first extraction zone, separating from the second extract phase a non-paraiiinic low boiling extract, introducing at least a' portion of said lover boiling extract into the first extraction raffinate and extract phases, separating the firstA raninate and extract phases, contacting the iirst extract phase in a second extraction zone with a low boiling"mineral oil distillate containing paraffinic and non-parailinic components under conditions causing the formation of a second `rainate phase comprising paraiiiic components of the said oil and of the low boiling distillate, and a second extract phase comprising non-parafnic components of the said oil and of the low boiling distillate, separating the second extract phase from the second ramnate phase, removing from the second raffinate substantially all of the low boiling distillate, returning at least the high boiling oil constituent of the residual portion of said second ranate phase to the rst extraction zone, separating from the second extract phase a non-parafnic low boiling extract therefrom, introducing at least a portion of said separated low boiling extract into the first extraction zone near the point of introduction of the solvent, withdrawing the 'rst ranate phase from the first extraction zone, and separating from said first rafnatephase a fraction containing the paraiiinic component of the high boiling oil in concentrated form.

7. A process of separating mineral oil fractions containing parafiinic and non-parailinic components into two portions, respectively, more parainic and less paraflinic than the original fractions, comprising the stepsof extracting a high boiling oil in a :iirst extraction zone with a selective solvent having s. greater solvent power for non-parainic hydrocarbons than for paramnic hydrocarbons, thereby producing first raflinate and extract phases, separating the rst ralnate and extract phases, contacting the rst extract phase ,in a second extraction zone with a low boiling mineral oil distillate containing parailinic and non-paraffinic componentsunder conditions causing the formation of a second raflinatephase comprising para'inic components of the said oil and of the low boiling distillate, and a second extract phase comprising non-paraihnic components of the said oil and of the low boiling distillate, separating the second extract and railnatev third railinate phase substantially all of the low boiling distillate, returning at least the high boiling oil constituent of the residual portion of the third raihnate phase. to the rst 'extraction roue, .withdrawing the first railinate phase from the, A, iirst extraction zone, and separating from said iirst rafilnate phase a fraction containing the parainic component of the high boiling oil in concentrated form.

8. A process of separating mineral oil fractions containing parailinic and non-,parailinic components into two portions, respectively, more paraflinic and less parailinic than the originalfractions, comprising the steps of extracting a high boiling oil in a first extraction zone in countercurrent with a selective solvent having a greater solvent power for noni-parainic hydrocarbons than for parafiinic hydrocarbons, thereby producing first raiinate and extract phases, separating the rst raffinate and extract phases, contacting the rst extract phase in a second extraction zone with a low boiling mineral oil distillate containing paraflinic and non-paranic components under conditions causing the formation of a. second raffinate phase comprising parainic components of the said oil and of the low boiling distillate, and a second extract phase comprising non-paraiiinic components of thev said oil and of the low boiling distillate, separating the second extract and ramnate phases, separating from the second extract phase a non-parainc low boiling extract, introducing at least a portion of said separated low boiling extract into the first extracon zone near the point of introduction of the solvent, extracting the second raiiinate phase in a third extraction mno with said selective solvent under conditions causing the formation of a third raiiinate phase and a third extract phase, separating the third extract and rainate phases, removing from the third raffinate phase substantially all of the low boiling distillate, returning at least the high boiling oil constituent of the residual portion of the third railinate phase to the first extraction zone near the point of introduction of the high boiling oil, withdrawing the first raiiinatephase from the extraction zone, and separating from said rst raffinate phase a fraction containing the paramnic component of thehigh boiling oil. in concentrated ferm.

9. A process of separating mineral oil fractions containing parafiinic and non-parailinic components into two portions, respectively, more paraiiinic and less paraiinic than the original fractions, comprising the steps of extracting a high boiling oil in a rst extraction zone in countercurrent with a selective solvent having a greater solvent power for 'non-parainic hydrocarbons than for paranic hydrocarbons,- thereby producing first raflinate and extract phases, separating the rst raffinate and extract phases, contacting the irst extract phase in a second extraction zone with a low boiling mineral oil distillate containing paraflinic and non-paranic components under conditions causing the formation oi a second raffinate phase comprising parafiinic components of the said oil and of the low boiling distillate, and a second extract phase comprising non-paraihic components of the said oil and of the low boiling distillate, separating the second extract and ranate phases, separating from the second extract phase a. non-parailiniclow boiling extract, introducing at least a portion of4 said separated low boiling extract into 'the rst extraction zone near the point of introduction of the solvent, extracting the second rafiinate phase in a third extraction zone with said selective -solvent lmder conditions causing the formation of a third railinate phase and a third extract high boiling oil in concentrated form.

extract the high boiling mineral oil, removing from the third ramnate phase substantially all of the low boiling distillate, returning at least the high boiling oil constituent of the residual portion of the third rafiinate phase to the -flrst extraction zone near the point of introduction of the high boiling oil, withdrawing the first rainate phase from the extraction zone, and separating from said first raiilnate phase a fraction containing the paraiiinic component of theA 10. A process of separating mineral oil fractions containing parafinic an non-paraifinic cornponents into two portions, respectively, more paramnic and less parafiinic than the original fractions comprising the steps of extracting a high boiling oil in a first extraction zone in countercurrent with a selective solvent having a greater solvent power for non-paratilnic hydrocarbons than forparafiinic hydrocarbons, thereby producing first rafiinate and extract phases, separating the first raffinate andv extract phases,

contacting the rst extract phase in a second extraction zone with a low boiling mineral oil distillate containing paraii'inic and non-paralnic components under conditions causing the formation ot a second railinate phase comprising paraiilnic components of the said oil and of the low boiling distillate, and a second extract phase comprising non-parafiinic components of the said oil and of the low boiling distillate, separating the second extract and raiiinate phases, returning the second ramnate phase to the first extraction zone near the point of introduction of the high boiling oil, separating from the second extract phase a non-paratiinic low boiling extract, introducing at least a portion of said extract into the first extraction zone near the point of introduction of the solvent, withdrawing the first raiiinate phase from the rst extraction zone, extracting at least a portion of said rst rafiinate phase in a third extraction zone with a selective solvent having a greater solvent power for non-parafiinic hydrocarbons than for parafnnic hydrocarbons under conditions causing the formation of third ratinate and extract phases separating the third raiiinate and extract phases, introducing at least a portion of the third extract phase into the first extraction zone at a point to cause it to flow countercurrently to the high boiling mineral oil,

and separating from the third raiiinate phase a fraction containing a paramnic low boiling ramnate.

ll. A process of separating mineral oil fractions containing parafllnic and non-parafflnic components into two portions, respectively more parainic and less parailinic than the original fractions comprising the steps of extracting a high boiling oil in a first extraction zone in countercurrent with a selective4 solvent having a greater solvent power for non-paraflinic hydrocarbons .than for parainic hydrocarbons, thereby producing first raillnate and extract phases, separating the rst ranate and extract phases, contacting the first extract phase in a second extraction zone witha low boiling mineral oil distillate containing paranlnic and non-paraiilnic components under conditions causing the formation of a second ralnate phase comprising parafiinic components of the said oil and'of the low boiling distillate, and a second extract phase comprising non-paraiiinic components of the said oil and of the low boiling distillate, separating the vsecond extract and raiiinate phases, returning the second rafiinate phase to the first extraction zone near the point of introduction of the high boiling oil, separating from the second extract phase a non-paraffinic low boiling extract, introducing at least a portion of said extract into the first extraction zone' power for non-para'lnic hydrocarbons than for v paraflinic hydrocarbons under conditions causing the formation of third ramnate and' extract phases separating the third rafilnate and'extract phases, introducing at least a portion of the third extract phase into the rst extraction zone at a point to cause it to flow countercurrently to the high boiling mineral oil,l and separating from the third raflinate phase a fraction containing a paraiiinic low boiling raffinate.

SIJBREN TlJMsTRA. 

